Raman Lidar Descriptions of Lower Atmosphere Processes
Document ID: 155
The Pennsylvania State University, Department of Electrical Engineering, University Park, PA, U.S.A.
Presented: Twenty First International Laser Radar Conference (lLRC21)
Québec, Canada, 8-12 July 2002
Abstract
Raman lidar provides vertical profiles or most of the key parameters needed to analyze and forecast the meteorological conditions, and to investigate processes controlling air quality in the lower atmosphere. The time sequence of atmospheric profiles is most valuable in understanding the meteorological processes controlling the evolution of air pollution events. The vibrational and rotational Raman lidar signals provide simultaneous profiles of meteorological parameters of temperature and water vapor, as well as the air quality parameters of ozone and airborne particulate matter. The LAPS (Lidar Atmospheric Profile Sensor) developed in 1995 was the first operational prototype Raman lidar instrument. It makes use of 2nd and 4th harmonic generated laser beams of a Nd:YAG laser to provide both daytime and nighttime measurements of atmospheric properties. The Raman scatter signals from vibrational states of water vapor and nitrogen provide robust profiles of the specific humidity in the lower atmosphere. The temperature profiles are measured using the ratio of rotational Raman Signals at 5.10 and 528 nm, and the temperature profile is combined with the specific humidity measurements to calculate profiles of relative humidity and RF refractivity. In addition, profiIes of optical extinction are determined from the gradients in the measured profiles of each of several molecular profiles. Wavelengths at 284 nm, 530 nm and 607 nm are used routinely to determine profiles of optical extinction, The ozone profiles in the lower troposphere are measured using a DIAL analysis of the ratio of the vibrational Raman signals from nitrogen (284 nm) and oxygen (278 nm), which are on the steep side of the Hartley band of ozone. Examples from several data sets are provided to demonstrate the utility of Raman lidar as a tool to provide the data needed by the meteorology and air quality communities, and to show the improved level of understanding of atmospheric processes that is gained from applications of lidar techniques.
| Citation: | "Raman Lidar Descriptions of Lower Atmosphere Processes", Philbrick, C. R., Lidar Remote Sensing In Atmospheric and Earth Sciences, Defence R&D Canada, 2002, pp. 535 - 545 |